LXR linux/arch/hexagon/kernel/process.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * Process creation support for Hexagon
   4 *
   5 * Copyright (c) 2010-2012, The Linux Foundation. All rights reserved.
   6 */
   7
   8#include <linux/sched.h>
   9#include <linux/sched/debug.h>
  10#include <linux/sched/task.h>
  11#include <linux/sched/task_stack.h>
  12#include <linux/types.h>
  13#include <linux/module.h>
  14#include <linux/tick.h>
  15#include <linux/uaccess.h>
  16#include <linux/slab.h>
  17#include <linux/resume_user_mode.h>
  18
  19/*
  20 * Program thread launch.  Often defined as a macro in processor.h,
  21 * but we're shooting for a small footprint and it's not an inner-loop
  22 * performance-critical operation.
  23 *
  24 * The Hexagon ABI specifies that R28 is zero'ed before program launch,
  25 * so that gets automatically done here.  If we ever stop doing that here,
  26 * we'll probably want to define the ELF_PLAT_INIT macro.
  27 */
  28void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
  29{
  30        /* We want to zero all data-containing registers. Is this overkill? */
  31        memset(regs, 0, sizeof(*regs));
  32        /* We might want to also zero all Processor registers here */
  33        pt_set_usermode(regs);
  34        pt_set_elr(regs, pc);
  35        pt_set_rte_sp(regs, sp);
  36}
  37
  38/*
  39 *  Spin, or better still, do a hardware or VM wait instruction
  40 *  If hardware or VM offer wait termination even though interrupts
  41 *  are disabled.
  42 */
  43void arch_cpu_idle(void)
  44{
  45        __vmwait();
  46        /*  interrupts wake us up, but irqs are still disabled */
  47        raw_local_irq_enable();
  48}
  49
  50/*
  51 * Copy architecture-specific thread state
  52 */
  53int copy_thread(unsigned long clone_flags, unsigned long usp, unsigned long arg,
  54                struct task_struct *p, unsigned long tls)
  55{
  56        struct thread_info *ti = task_thread_info(p);
  57        struct hexagon_switch_stack *ss;
  58        struct pt_regs *childregs;
  59        asmlinkage void ret_from_fork(void);
  60
  61        childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) -
  62                                        sizeof(*childregs));
  63
  64        ti->regs = childregs;
  65
  66        /*
  67         * Establish kernel stack pointer and initial PC for new thread
  68         * Note that unlike the usual situation, we do not copy the
  69         * parent's callee-saved here; those are in pt_regs and whatever
  70         * we leave here will be overridden on return to userland.
  71         */
  72        ss = (struct hexagon_switch_stack *) ((unsigned long) childregs -
  73                                                    sizeof(*ss));
  74        ss->lr = (unsigned long)ret_from_fork;
  75        p->thread.switch_sp = ss;
  76        if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
  77                memset(childregs, 0, sizeof(struct pt_regs));
  78                /* r24 <- fn, r25 <- arg */
  79                ss->r24 = usp;
  80                ss->r25 = arg;
  81                pt_set_kmode(childregs);
  82                return 0;
  83        }
  84        memcpy(childregs, current_pt_regs(), sizeof(*childregs));
  85        ss->r2524 = 0;
  86
  87        if (usp)
  88                pt_set_rte_sp(childregs, usp);
  89
  90        /* Child sees zero return value */
  91        childregs->r00 = 0;
  92
  93        /*
  94         * The clone syscall has the C signature:
  95         * int [r0] clone(int flags [r0],
  96         *           void *child_frame [r1],
  97         *           void *parent_tid [r2],
  98         *           void *child_tid [r3],
  99         *           void *thread_control_block [r4]);
 100         * ugp is used to provide TLS support.
 101         */
 102        if (clone_flags & CLONE_SETTLS)
 103                childregs->ugp = tls;
 104
 105        /*
 106         * Parent sees new pid -- not necessary, not even possible at
 107         * this point in the fork process
 108         */
 109
 110        return 0;
 111}
 112
 113/*
 114 * Release any architecture-specific resources locked by thread
 115 */
 116void release_thread(struct task_struct *dead_task)
 117{
 118}
 119
 120/*
 121 * Some archs flush debug and FPU info here
 122 */
 123void flush_thread(void)
 124{
 125}
 126
 127/*
 128 * The "wait channel" terminology is archaic, but what we want
 129 * is an identification of the point at which the scheduler
 130 * was invoked by a blocked thread.
 131 */
 132unsigned long __get_wchan(struct task_struct *p)
 133{
 134        unsigned long fp, pc;
 135        unsigned long stack_page;
 136        int count = 0;
 137
 138        stack_page = (unsigned long)task_stack_page(p);
 139        fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp;
 140        do {
 141                if (fp < (stack_page + sizeof(struct thread_info)) ||
 142                        fp >= (THREAD_SIZE - 8 + stack_page))
 143                        return 0;
 144                pc = ((unsigned long *)fp)[1];
 145                if (!in_sched_functions(pc))
 146                        return pc;
 147                fp = *(unsigned long *) fp;
 148        } while (count++ < 16);
 149
 150        return 0;
 151}
 152
 153/*
 154 * Called on the exit path of event entry; see vm_entry.S
 155 *
 156 * Interrupts will already be disabled.
 157 *
 158 * Returns 0 if there's no need to re-check for more work.
 159 */
 160
 161int do_work_pending(struct pt_regs *regs, u32 thread_info_flags)
 162{
 163        if (!(thread_info_flags & _TIF_WORK_MASK)) {
 164                return 0;
 165        }  /* shortcut -- no work to be done */
 166
 167        local_irq_enable();
 168
 169        if (thread_info_flags & _TIF_NEED_RESCHED) {
 170                schedule();
 171                return 1;
 172        }
 173
 174        if (thread_info_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) {
 175                do_signal(regs);
 176                return 1;
 177        }
 178
 179        if (thread_info_flags & _TIF_NOTIFY_RESUME) {
 180                resume_user_mode_work(regs);
 181                return 1;
 182        }
 183
 184        /* Should not even reach here */
 185        panic("%s: bad thread_info flags 0x%08x\n", __func__,
 186                thread_info_flags);
 187}
 188